Helicopter lifting screw operating mechanism



A, A. LOCKE March},- 1"948.-

' HELICOPTER LIFTING SCREWv OPERATING MECHANISM FiledApii} 27, 1944 s Sheets-Sheet 1 INVENTOR ARTHUR A. LOCKE mym ATTORNEY A. LOCKE 2,437,165

HELICOPTER LIFTING SCREW OPERATING MECHANISM Mdrh 2, 1948.

5 Sheets-Sheet 2 File April 27, 1944 IN V EN TOR. ARTHUR A LOCKE fin /W ATTCRNE Y A. A. LOCKE v 2,437,165

HELICOPTER LIFTING SCREW OPERATING MECHANISM March 2, 1948.

Filed April 27, 1944 5 Sheets-Sheet 3 INVENTOR. ARTHUR A. LOCKE f? ATTORNEY Patented Mar. 2, 1948 UNITED STATES m1151w OFFICE HELICOPTER LIFTING SCREW OPERATING MECHANISM Arthur .A. Locke, Detroit, Mich.

Application April 27, 1944, Serial No. 532,981

This invention relates, to helicopters, or direct hit aircraft, and in particular, it relates to the rotor hub for sustaining vertical screw blades of a helicopter type aircraft. More particularly, the invention relates to a directliftaircraft embodying co-axial contrarctating air screw blades in combination with direct manualmeans for varying the angle ofincidencebf the blades, or for effecting cyclic pitch control.

It is recognized that co-axial contra-rotating blades have heretofore been disclosed and demonstrated. However; the successful application of such a type of direct lift aircraft depends principally upon means forv controlling the pitch of the blades to within critical limitations. If the angle of incidence of the blades throughout their useful range of operation is not properly maintained, the aircraft becomes subjected to objectionable vibration and" is difficult to control in flight. In accordance with the practice of my invention, I provide c'o-axi'al and. contra-rotating airscrew blades in which the angle of incidence may be manually and positively controlled over a wide range of operating conditions so as to present eachbladein an optimum efiicient position with the relative wind. By maintaining positive control of the, angle of incidence of the blades throughout their cycle of operation, many advantages accrue. In the first place, the contra-rctating blades provide automatic torque compensation. thus utilizing all available power for lift or directional flight. Also; the double set of blades, as compared'with' a single set of blades, permits a; substantial reduction, in blade span.

Incombination with these-features; it is among the objects of my invention toprovide positive blade-pitch control and variable cyclic pitch control; to provide a positive and uniform desired angle of incidence for direct ascent; to provide pitch control over one set of blades and a. complem'entary opposite pitch inclination of the oppositely rotating set: of blades; to provide means in the form of a singlecontrol'through' which the various changes in pitch" result; to provide an ehicient and dependable means for-actuating and maintaining the angle of'incidence ofthe' blades; and to provide a mechanism which is light in weight and economical of manufacture.

These and other objects and advantages of my invention will appear morefully in the'folloW-' ing detailed description-when considered in connection with the accompanying drawing; in which:

Figure l is a perspectiveviewbf arotor'head. of myinvention;

11 Claims. (Cl. 24417) Figure 2 is a longitudinal view, in section.- of the embodiment illustrated in Figure 1, except that the upper and lower sets of blades are illustrated in alignment;

Figure 3 is a transverse view, in section, taken along lines III"III of Figure 2; and

Figure 4 is a transverse view, in section, taken along lines IV IV of Figure 2.

With reference to the drawings and in particular to Figures 1 and 2, the invention consists of a rotor'head comprising essentially a pair of tubular co-axial drive shafts H and I2 attached at their lower ends to bevel gears l3 and M, respectively. A frame supports the gears and the vertical tubular shafts I I and I2. The frame I 5 may be a part of or attached to the structural members of the helicopter. A hub l6 forming a part of the frame 15 forms a housing for supporting roller bearings I] and is, a" spacer ring I9 and a bearing retainer The bearings 11 and I 8-, in turn. support a shaft 2-I'- to whichis keyed a bevel drive gear 22' which meshes with the bevel gears Band II. The shaft 2| extends to any suitable means for generating power. Diametrically opposite the-gear 22 is a similar bevel gear 23 constituting an idler interposed between the bevel gears l3 and IA and supported by the frame l5 through a shaft 24'. By this arrangement, operation of the shaft 2| causes the tub'uflar drive shafts H and l 2 to rotate in opposite di-' rections;

The tubular shaft H is supported at its lower end by a roller bearing 25, mounted in a hub 26, forming part of the frame l5. A retaining member 2! maintains the bearing 25 in proper relative position. At the upper end of the frame I5 is a roller bearing 28, mounted in a hub 29, forming part of the frame [5. The bearing 28 is held in place by a retaining'member 30, and a flange 3| atttached to the tubulardrive' shaft I2 also engages the bearing; A similar bearing 32 andretainer 33 function to support the lowermost portion of the tubulardriveslia'it' I21 Attached to the upper end of the tubular drive shaft 12 is a hub" 34 having'ar'ms 35 extending therefrom. This hub and arm combination supports a horizontally positioned tubular member iii-which, in turn, is attached to and supports a blade '37. Bearings 38 and 39 are interposed'between the tubular'me'mber 36 and the hub and arm combination. By this arrangement the blade 31 is free to pivot on the axis of the tubular member 36. At-the inward end of the member 36' is a nut 40' Whichrestricts outward movement of the member 36; similar blade and 'tioned axially within the sleeve-59.

from. In a similar manner to the hub 34 and arm." 35, the present hub 43 and arm 44 combination,

functions to support a horizontal tubular member 45, through bearings, and a, vertical screw blade 46. This upper blade unit also constitutes a pair of blades 46 diametrically opposed.

A control mechanism is provided for impart-" ing rotary motion to the tubular member 45in order to vary the angle of incidence of the blade 46. This is accomplished by alever mechanism extending through the tubular shaft II. More particularly, a collar 41 is'attached to'the tubular member 45, and vertically extending pins. 48 project from the collar. An arcuate arm 49 (Figure 1) pivotally associated with the pin 48, extends in asubstantiallyhorizontal direction over an angle of about 90 degrees where itcon'nects to a vertical link 59, through'a ball and socket joint The connecting link 59 is pivotally at- I tached at 52 toar arm 53 supported by a lever 5,4,,through ball bearings 55. By this arrangement, the arm 49 connecting link56' andarm 53 rotate with the tubular drive shaft "While the lever 54 does not rotate. Alsimilar arm 58ccoperates with the diametrically opposed blade assembly. I 7 r i r v The angle of incidence of the blades 46" may be varied by moving the lever '54 in an axial direction. As shown in Figures 2 and '3, the lever 54 is pivotally attached to agimbal ring 56-by means of a pin 51. The gimbal ring, in turii, is pivotally pinned at 58 to a sleeve 59 lying within the tubular drive shaft II. The pivot 58'is located in a position measuring 90 degrees from the lever pin 51. A bushing 69 pressed onto the end of the sleeve 59 is slidable within the tubular drive shaft II. A similar bushing 6| is located at the lowermost portion of the tubular drive shaft I l'. A flange 62, attached, to the lower end of the sleeve 59, cooperates with means, hereinafter described, for raising or lowering the sleeve 59. This move-- ment, in turn, raises or lowers the lever 54 'aXially of the assembly, thus imparting arotary motion to the tubular member 45 for varying the angle of incidence of the blades 49.

While a direct vertical movement of the lever 54 results in imparting a uniform change in angle of incidence of the various blades, the angle of incidence may be changed in such manner as to provide cyclic pitch controL- lfhis is effected by tilting the lever "54 in-the desired direction. To effect the tilting operatioman arm 83 extends downwardly from the lever 54. This arm 63 terminates with a spherical end 64 contacting a cam plate 65 attached to the end of a sleeve 66 posi- The cam plate 65 takes the form of abeveled end surface of the sleeve 66. A bushing 6'! is pressed onto the sleeve 66'near its upper end, and is slidable within thejsleeve 59. A similar bushing 69 located near the lower end'of the sleeve 66 maintains the sleeve 66 in slidable relation with the sleeve 59.

In order to actuate the lever 54 to accommodate its various functionait is necessary thatthei sleeves 59 and 66 be axially slidable, independent of each other, and that the sleeve 66 be rotatable over a range of substantially 180 degrees. All of these movements may be accomplished through the operation of a single control wheel 69. The wheel 69 is attached to a sleeve 19 rotatable about a lever H. The lever, in turn, is pivotally pinned at 72 to a bracket 73, and the bracket, in turn, is pivoted axially of the assembly by means of a stud 14 secured to an extension member '15 of the main frame l5. An arm 16 forming an eX- tension of the lever ll pivotally engages with a irl'g 'movement of the hand wheel 69 results in a vertically reciprocal movement of the sleeve 66. Also a horizontally swinging movement of the hand-wheel 69'causes a rotating movement of the sle,eve;66,,.1 To obtain the vertical movement of the sleeve 59, a cam 18 is provided for engagement with the flange 62. The cam is attached to the sleeve 19 and is shaped radially in respect to the pivot 12" so that vertical swinging movement of the hand wheel 69 will not interfere with the vertical movement of the sleeve 59. It is also obvious that horizontal swinging movement of the hand wheel 69 will not affect movement of the sleeve 59. The cam 18, however, assumes a cam profile in respect to a plane transversely of the axis of the lever 1! ate. point in alignment with the pivot l2.- By such a construction, rotary movement of the hand wheel 69 will set the cam 18linto" operation so as to raise or lower the flange 62 and,consequently, the sleeve 59. The sleeve 59 and'its associatedmechanism is of suihcient weight so that theflange 62 will always lie in contact "relation with the cam 18. As thus described, it is apparentthat three separate and distinct movements .of the hand wheel 69 may be operated, independently, or simultaneously, to efifect selective operable movement of either or both of the sleeves 59 and 66.

To prevent unnecessary rotation of the sleeve .59',.due to its adjacent engagement with the tubular drive shaft II, a pin 79 is attached to the sleeve 59. and is slidable in a slot 89 extendingalong a length of the sleeve 66. As thus far described, means have been provided for the structure and operation of the upper set of blades. Itis necessary to transfer a complementary and opposite angle of incidence to the lower set of blades which are rotating in an opposite directionf All of these. movements are transferred from the upper set of blades to the lower set of blades initially through the connecting link 59. A gimbal unit 8! is employed for transferring this movement to oppositely rotating sets of blades. The gimbal unit 8| is shown particularly in Figures 1 and-4. It includes a-hub 82 having bushings 83 pressed internally at the ends thereof, the bushings being slidable along the tubular drive shaft IL' Bosses 84 project from the hub 82' at-diametrically opposed positions for pivotally supporting through studs 86 a gimbal ring 86." At a position measuring 90 degrees from the studs 85, another set of pivot studs 87, also diametrically opposed, connect the gimbal ring with a transfer ring 88. Loosely positioned around the transfer ring are upper and lower discs 89 and- 99, respectively. These discs are separated from each other and from the ends of the transfer ring by ball thrust bearings 9!. A retainer 92 threaded onto the transfer ring 88 clamps the ball thrust bearings 9| and the discs 89 and 99 in a position to permit free rotary v 'set of :blades.

f zmovementyofcthadiscs 89 and;90. .Fllhe. discr89is provided with annex-tension 193,- and theconnecting .link eSIIrthrough: a I wide hub 94, -is pivotally attached to; the'tubular member as, thus-movement of thea'arm 99 functionsto control the angle of incideneepf the lower set-of blades.

.In..the-operationqofthe:ro-tor head, the tubularrshaf-ts l-: and- I2 :rotate inan opposite. direction, thusdriving in: opposite diiectlons'the up- ,perrandjower-setsof blades. As shown in Figure..-1,..the upper set of blades rotate in a clockwise-directionclooking downwardly on the'rotor -:head. iuThelower set ofb1a:des rotate in a :countereclockwise direction. .Theremaining operative :mechanism 'is concerned principally with the manual control .of angle "of incidence .of the blades. As the helicopter rests upon thezg'round :the :blades T3136 p'ositionedin a neutral or nega- ":tllke tangle of: incidence. ;If itris desired to cause 'vertical Iascent' of i the helicopter the ipilot .operates the hand-wheel '.69.in1a turning motion so ;that"the.icam :18 elevates the flange 62. This,

in Lturnnmoves ;the.:sleeve :59' in an .upwardposi- 'tion,;carryirrgwith itath'elleverili l. :By means-Jot the arm :53 and 1 connecting. link 50, :theiarcuate '=arm :49;:is actuated ;.so.:as to increasetheangle .or incidence-"ofthe.upperiset of blades. Upward :movementiof the 'conneetinglinlz 5E8 alsooperates ,torcau'se' the *gimbal unit: 8 i .to .slidexupwardlyz on :the tubularcdrivesshaft: l l .In-its upward move- 1nent,".-the:gimbal .unit carries with it thecon- .nectingdink .B'Lthus actuating the arm 599 for increasing the angle of .incidence'of the lower set of blades. 'Thus, it is apparent *that'rotary'move- :ment'of the hand wheel 69 will result in a'uniform controlrof the angle of incidence of boththe 1 uppe'rzand; lower setsitof blades, and :that :this uniiform'chan'ge intheiangle of incidence of allthe iblades is accomplished notwithstanding the diftficulty :tof transmitting similar motions .from a set of blades operating in one direction to .a "set of-blades operating in an oppositedirection. It is to be understood that the lower :set'of :blades may have a. greater'pitch .thanithe upper .This i is "of advantage because :the velocity of the relative wind is greater with respectto the .lowersetrof blades due to theslipstream resulting fromthe upper set of blades.

.Inorder'to accomplish flight'in a horizontal direction, it is necessary to vary the'angle of incidence of the blades, depending upon the positionofxea-ch blade as-it isrotated. In-other 'words,'a cyclic pitchcontrolis required-in which the foremost bla'dein tthe directionofflighthas aFsubstan'tiaIly.neutral.'anglenf incidence, where- :as the :blade :in :a substantially Laft position assumesza irelativelyihigh angle .of incidence. The blades, when :assuming a lateral position relative to the direction of flight, :also require :a dif- 'ferent angle of incidence;' that.is,'the retreating "blade has a higher angle of incidence than the advancing blade. This cyclic pitch control is obtained :manually by the operator by :merely #swinging the-hand wheel GBso that it"willmove about the pivot 12. This results in an axial movement of the sleeve lib causing the cam S65 -to-deflect'the-sph'erical ball 64 off .of its normal ii fcentralrposltion. lThr'oug'hthevgimbal ring 56, the lever umayfibatiltediinrany desired direction. This iitiltin'g iofthelever's54 generally results'lin an' mcreasejrinthe angle of incidence of zone ofithe blades, and a lesser or neutral angle of 1 incidence .of aits diametrically iopposed blade. The gimbal'qmitfl alsotilts in any desired direction, thus, resdlting'in a corresponding varianc in the angle "ofincidence of the lower set of blades. "Therefore, by merely swinging the hand 'wheel"'69- about the pivot 12 a cyclic pitch control is *flected for inducing horizontal flight. While'tlie c'yclic pitch'control is in efiect, a furtherincre'ase or decrease in the angle of incidenceoi'all of the blades may be obtained by merely rotatingthehand wheel'fill. While this control maybe operated entirely independent of the-cyclic pitch control'it,"nevertheless, may be operated simultaneously therewith.

The direction ofhori'zontal .fiight may be selected by thepllotby swinging the hand wheel '69 so that itmoves about the pivot M. "This action ir'nr'iaifts rotary movement to the sleeve 66 which deterniinesfthe direction of tilt of the lever 54. "The operation or the hand wheel 69 about .the pivot .14, "therefore, determines the position .whe'reat the .greater .or lesser angle of incidenceLoccurs .in the .cycle io'f rotation of the blades and, accordingly, determines the direction of fiightbfthealrcirdft.

.Thecontrol-whehfl ,thus operates a uniform changezin vthe'ang'leof incidence of all the blades,

effects .a: cycl ielpitch .control, and permits selectivedirectional flight. ,These three control ope-r ations -may .eachbeeffectedlindividually, or they maybe operated simultaneously in any combinetion-desired.

As thus shown =:and .described, it is believed apparent that I haveyprovided a;novel and uni- .que arrangement-ofparts and controls therefor, for. the constructionzand;operation of a helicopter I in whlchasimplicity is-obtained in the constructionand.function ofiafcomplex operation in the change of the ,angleof'incidence throughout its entire useful range of operation. While I'have described a preferred embodiment of my invention, it is :to beiunderstood that it is susceptible of those modifications :which appear obviously s'crew bl'ade's supported t'and'rotated by the drive shaft, said :blades being movable to permit variatio'min angle ofincidencean arm adaptable for movement :ffor-:changing the angle of incidence tofzeach blade, :means extending axially through #the drive shaft and engage'able with said arm,

m'eanssoperable by a pilot to impart axial movemerit toithelri'e'ans iextending through the drive shaft, Fsa'id meanseXtending through the drive shaft rb'eing :tiltable in part for simultaneously l'efie'cting a different angle :of incidence of the different blades, and means operable .by a pilot comprisingamemberadaptable for vertically reciprocal Tand, rotatable movement extending throughsaid second named means ior both positioning and actuating said tiltable portionin a directionally-selected'manner, each of said pilot operatinglmeans constituting a combined manual control (and .ibeing actuable simultaneously or'independently.zforaeffecting a uniform change in angle of incidence or a. different change in angle of incidence of the different blades.

2. In a helicopter, a hollow drive shaft, air screw blades supported and rotated by the drive shaft, said blades being movable to permit variation in angle of incidence, an armadaptable for movement for changing the angleofincidence of each blade, means extending axially through the drive shaft and engageable withsaid arm, means operable by a pilot to impart axial movement to the means extending-through the drive shaft, said means extending through the drive shaft being tiltable in part forsimultan-eously effecting a different angle of incidence of the different blades, means operable by a pilot comprising a member adaptable for. vertically reciprocal and rotatable movement extending through said second named means for both positioning and actuating said tiltable portion, and means operable by a pilotfor selecting the direction of tilt of said tiltable portion.

8. In a helicopter, a hollow drive shaft, air screw blades supportedjand rotated by the drive shaft, said blades being movable'to permit variation in angle'of incidence, an arm adaptable for movement for changing the angle of incidence of 'each blade, means extending axially through the drive shaft and engageable with said arm, means operable by a pilot to impart axial movement to the means extending through the drive shaft, said means extending through the drive shaft being tiltable in part for simultaneously eflecting a diiferent angle of incidence of the diiferent blades, means operable by a pilot comprising a member adaptable for vertically reciprocal and rotatable movement extending through said second named means for both positioning and actuating said tiltable portion, and means operable by a pilot for selecting the direction of tilt of said tiltable portion, each of said pilot operating means constituting a combined manual control and being "actuable simultaneously or independently for effecting a uniform change in angle of incidence or a different change in angle of incidence of the different blades.

4. In a helicopter, a hollow drive shaft, air screw blades supported and rotated by the drive shaft, said blades being movable to permit variation in angle of incidence, an arm adaptable for movement for changing the angle of incidence of each blade, means extending axially through the drive shaft and engageable with said arm, means operable by a pilot to impart axial movement to the means extending through the drive shaft, said means extending through the drive shaft being tiltable in'part for simultaneously effecting a different angle of incidence of the different blades, means operable by a pilot comprising a member adaptable for vertically reciprocal and rotatable movement extending through said second named means for both positioning and actuating said tiltable portion in a directionally selective manner, a second drive shaft positioned coaxially of said first drive shaft and rotatable in opposite direction, air screw blades supported and rotated by the second drive dence of each blade, means extending axially through the drive shaft and engageable with said arm, means operable by a. pilot to impart axial movement to the means extending through the drive shaft, said means extending through the drive shaft being tiltable in part for simultaneously eifecting' a different angle of incidence of the different blades, means operable by a pilot comprising a member adaptable for vertically reciprocal and rotatable movement extending through said second named means for both positioning and actuating said tiltable portion in a directionally selective manner, each of said pilot operating means constituting a combined manual control and being actuable simultaneously or independently for effecting a uniform change in angle of incidence or a different change in angle of incidence of the different blades, a second drive shaft positioned coaxially of said first drive shaft and rotatable in opposite direction,

' air screw blades supported and rotated by the shaft, and means for transferring the angle of second drive shaft, means for transferring the angle of incidence movement from one set of blades to the other and oppositely rotating set of blades.

6. In a helicopter, a'hollow drive shaft, air screw blades supported and rotated by the drive shaft, said blades being movable to permit variation in angle of incidence, an. arm adaptable for movement for changing the angle of incidence of each blade, means extending axially through the drive shaft and engageable with said arm, means operable by a pilot to impart axial movement to the means extending through the drive shaft, said means extending through the drive shaft being tiltable in part. for simultaneously effecting a different angle of incidence of the different blades, means operable by a pilot comprising a member adaptable for vertically reciprocal and rotatable movement extending throughisaid second named means for both positioning and actuating said tiltable portion, means operable by a pilot for selecting the direction of tilt of said tiltable portion, a second drive shaft positioned coaxially of said first drive shaft and rotatable in opposite direction, air screw blades supported and rotated by the second drive shaft, and means for transferring the angle of incidence movement from one set of blades to the other and oppositely rotating set of blades.

'7. In a helicopter, a hollow drive shaft, air screw blades supported and rotated by the drive shaft, said blades being movable to permit variation in angle of incidence, an arm adaptable for movement for changing the angle of incidence of each blade, means extending axially through the drive shaft and engageable with said arm,'means operable by a pilot to impart axial movement to the means extending through the drive shaft, said means extendin through the drive shaft being tiltable in part for simultaneously effecting a different angle of incidence of the difierent blades, means operable by a pilot comprising a member adaptable for vertically reciprocal and rotatable movement extending through said second named means for both p0- sitioning and actuating said tiltable portion, means operable by a pilot for selecting the direction of tilt of said tiltable portion, each of said pilot operating means being actuatable simultaneously or independent of each other, a second drive shaft positioned coaxially of said first drive shaft and rotatable in opposite direction, air screw blades supported and rotated by the sec- 9 nd drive shaft, and means for transferring the angle of incidence movement from one set of blades to the other and oppositely rotating set of blades;

8. In a helicopter, a hollow drive shaft, air screw blades supported and rotated by the drive shaft, said blades being movable to permit variation in angle of incidence, an arm adaptable for movement for changing the angle of incidence of each blade, means extending axially through the drive shaft and engageable with said arm, means operable by a pilot to impart axial movement to the means extending through the drive shaft, said means extending through the drive shaft being tiltable in part for simultaneously effecting a different angle of incidence of the different blades, means operable by a pilot comprising a member adaptable for vertically reciprocal and rotatable, movement extending through said second named means for both positioning and actuating said tiltable portion, a second drive shaft positioned coaxially of said first drive shaft and rotatable in opposite dizrectlon, air screw :blades supported and rotated by the second drive shaft, means for transferring the angle of incidence movement from one set of blades to the other and oppositely rotating set of blades, said transferring means comprising an axially slidable gimbal track, arms cor-- necting the pilot operable means with the track, and means connecting the track with the said oppositely rotating set of blades.

9. In a helicopter, a hollow drive shaft, air screw blades supported and rotated by the drive shaft, said blades being movable to permit variation in angle of incidence, an arm adaptable for movement for changing the angle of incidence of each blade, means extending axially through the drive shaft and engageable with said arm, means operable by a pilot to impart axial movement to the means extending through the drive shaft, said means extending through the drive shaft being tiltable in part for simultaneously effecting a different angle of incidence of the different blades, means operable by a pilot comprising a member adaptable for vertically reciprocal and rotatable movement extending through said second named means for both positioning and actuating said tiltable portion, each of said pilot operating means being actuatable simultaneously or independent of each other, a second drive shaft positioned coaxially of said first drive shaft and rotatable in opposite direction, air screw blades supported and rotated by the second drive shaft, means for transferring the angle of incidence movement from one set of blades to the other and oppositely rotating set of blades, said transferring means comprising an axially slidable gimbal track, arms connecting the pilot operable means with the track, and means connecting the track with the said oppositely rotating set of blades.

10. In a helicopter, a hollow drive shaft, air screw blades supported and rotated by the drive shaft, said blades being movable to permit variation in angle of incidence, an arm adaptable for movement for changing the angle of incidence of each blade, means extending axially through the drive shaft and engageable with said arm, means operable by a pilot to impart axial movement to the means extending through the drive shaft. said means extending through the drive shaft being tiltable in part for simultaneously effecting a different angle of incidence of the different blades, means operable by a pilot comprising a member adaptable for vertically reciprocal and rotatable movement extending through said second named means for both positioning and actuating said tiltable portion, means operable by a pilot for selectin the direction of tilt of said tiltable portion, a second drive shaft positioned coaxially of said first drive shaft and rotatable in opposite direction, air screw blades supported and rotated by the second drive shaft, means for transferring the angle of incidence movement from one set of blades to the other and oppositely rotating set of blades, said transferring means comprising an axially slidable gimbal track, arms connecting the pilot operable means with the track, and means connecting the track with the said oppositely rotating set of blades.

11. In a helicopter, a hollow drive shaft, air screw blades supported and rotated by the drive shaft, said blades being movable to permit variation in angle of incidence, an arm adaptable for movement for changing the angle of inci dence of each blade, means extending axially through the drive shaft and engageable with said arm, means operable by av pilot to impart axial movement to the means extending through the drive shaft, said means extending through the drive shaft being tiltable in part for simultaneously effecting a different angle of incidence of the different blades, means operable by a pilot comprising a :member adaptable for vertically reciprocal and rotatable movement extending through said second named means for both p0- sitioning and actuating said tiltable portion, means operable by a pilot for selecting the direction of tilt of said tiltable portion, each of said pilot operating means being actuatalole simultaneously or independent of each other, a second drive shaft positioned coaxially of said first drive shaft and rotatable in opposite direction, air screw blades supported and rotated by the second drive shaft, means for transferring the angle of incidence movement from one set of blades to the other and oppositely rotating set of blades, said transferring means comprising slidable gimbal track, arms connecting the pilot operable means with the track, and means connecting the track with the said oppositely rotating set of blades.

. ARTHUR A. LOCKE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Austria Apr. 25, 1939 

